1. Field of the Invention
The present invention relates to a liner for a well bore, and more particularly, but not by way of limitation, to an improved apparatus and method for lining a casing affixed within a well bore.
2. Brief Description of Related Art
As the drilling of an oil or gas well progresses, the well bore is lined with a casing that is secured in place by a cement slurry injected between the exterior of the casing and the well bore. The casing commonly consists of steel tubulars joined by couplings and functions to provide a permanent well bore of known diameter through which drilling, production, or injection operations may be conducted. The casing also provides the structure for attaching surface equipment required to control and produce fluids from the well bore or for injecting fluids therein. In addition, the casing prevents the migration of fluids between subterranean formations through the well bore (e.g., the intrusion of water into oil or gas formations or the pollution of fresh water by oil, gas, or salt water).
Heat loss from produced fluids through the steel tubulars and couplings of the casing to the surrounding subterranean formations is relatively high due to the high thermal conductivity of steel and rock. Heat loss from the produced fluids can be problematic during production. For example, if a gas is produced through the steel tubulars, liquids condensing from the gas due to cooling can result in liquid dropout thereby causing a loss of valuable fluids and reducing the flow of the gas through the steel tubulars. Another problem may arise when temperature loss from the produced fluids induces the formation of scales, paraffin, or other deposits on the steel tubulars, thereby creating restrictions, or even a blockage, of the fluid flow through the steel tubulars.
Though vacuum insulated steel tubing offers sufficient insulation, heat loss from the couplings may reduce the total insulation quality significantly. Furthermore, couplings can create discontinuities along the flow path that result in increased friction and turbulence in the flow of produced fluids. Plastic liners have demonstrated insulation benefits and are more consistent than vacuum insulated steel tubing because they do not have couplings. Plastic liners are generally less expensive than vacuum insulated steel tubing; however, current plastic liners are not as effective in insulation benefits per foot as the vacuum insulated steel tubing.
A method of lining a casing with a continuous string of tubular polymeric material has previously been proposed. This method is disclosed in U.S. Pat. No. 5,454,419, issued to Jack Vloedman. The method disclosed in the Vloedman '419 patent utilizes a continuous, smooth walled polymeric tubular liner wound on a portable spool. The smooth walled liner has an outer diameter greater than the inner diameter of the casing and is reeled off the spool and through a roller reduction unit to reduce the diameter of the liner so that the liner can be injected into the casing. A weight system connected to the bottom end of the liner maintains the reduced liner in tension so that the liner remains in its reduced state until the liner is positioned at a desired depth. After the liner is run to such depth, the weights are removed thereby allowing the reduced liner to rebound and form a fluid tight seal with the casing and seal any breaches in the casing.
While the method disclosed in the Vloedman '419 patent has successfully met the need for lining and repairing breaches in a casing in an effective and time efficient manner, several inefficiencies have nevertheless been encountered, particularly when attempting to line a casing at depths below about 5,000 feet. In attempting to line a casing at depths below about 5,000 feet, the weight of the weight system coupled with the weight of the liner being run into the casing can cause the liner to plastically deform and exceed the yield strength resulting in permanent deformation.